1. Field of Invention
The present invention relates to a system and method for measuring a distance between two objects. More specifically, the present invention relates to a system and method of measuring a distance between two objects using RF techniques.
2. Description of the Related Art
Mobile telephones, pagers, and other wireless communication equipment are now commonplace. More recently, laptop computers, personal digital assistants (PDAs)—such as the Palm™ organizer—have been equipped with wireless communications capabilities. One of the primary benefits of wireless equipment is portability. We can carry our mobile phone with us wherever we go. These wireless devices are currently used for relatively limited purposes, such as making telephone calls, when they are capable of doing much more.
One potential use for wireless devices is in mobile commerce. Wireless devices can be used for buying or selling goods or services, making payments, gathering information, advertising and promotion, and the exchange of information for other commercial or non-commercial purposes. The success of mobile commerce and other wireless applications will depend on their acceptance by consumers at large. Accordingly, wireless applications must be easy to use and convenient. New platforms are being developed to enable mobile commerce and other applications for wireless devices. Bluetooth™ is such a technology. Bluetooth™ provides a wireless networking protocol for linking various wireless equipment, such as mobile computers, mobile phones, and PDAs. Bluetooth™ operates in the Industrial Scientific and Medical (ISM) 2.4 GHz region.
In addition to platforms such as Bluetooth™, wireless devices require additional enabling technologies to reach their full potential. One such technology involves distance measurement. The distance between two or more wireless devices may be needed in a variety of applications. In many cases, it may be undesirable to measure the distance between two wireless devices directly. Direct distance measurement may be impossible, impractical, intrusive, or simply inconvenient. Moreover, because one or more wireless devices may be moved, the distance between devices will not be fixed indefinitely and re-calculation may be needed.
In such situations, ‘wireless’ distance measurements are used. Some ‘wireless’ distance measurement systems require an infrastructure to be put in place such as GPS based systems, triangulation methods, and other positioning techniques. Other systems require line-of-sight conditions (e.g., infra red, laser, and optical methods). Radar as well as ultra sonic systems are bulky, complex, and consume significant amounts of power. New ultra wide band techniques are currently not approved by the authorities. Some less expensive systems offer solutions based on field strength measurements with the tradeoffs of reduced reliability and high environmental dependency.